This is a manga that has really good action that is incredibly cool a lot of the time. Mamoru as a swordsman is amazing, and seeing him deal with conventional weapons far beyond the scope of being dealt with a blade is amazing. As that begins to get old, a number of unique enemies are brought out that use strange weapons that have to be dealt with in special ways, which keeps things interesting. That holds up the core of the manga quite well. The plot overall, was a bit strange. It starts out pretty good, being well paced and at a scale that felt it fit the story. However, at some point, the pacing seemed to get inconsistent, where things began to escalate tremendously in terms of organizations and characters involved as well as in terms of scale, to the point it felt like a lot was being left out. I think that this may have had to do with the other mangas that are connected to this one, and hence I suppose it was a conscious choice that makes sense, however while this does work with comics, I feel it doesn't work as well with stories like this. Still, the plot was pretty fast moving and intense for the most part, though it felt like there were moments where it seemed to simply be messing around for no reason as well as a couple cheap moments, such as a deaths that felt forced, especially towards the end which felt kind of rushed. On that note, I would like to note that while the romance is apparently a pretty important aspect of the manga based on its self-description, and it certainly felt that way from the ending, it was not developed at all. By that I mean absolutely not at all. There was nothing. Zero. Nada. It seemed to pop up from time to time, but never in a way that was actually developed, so even though I'm fine with it and think it is the right way to take the story, how it just worked out in the end felt weak. Other than that, Mamoru is a really cool character that got developed really well, especially in regards to back story. Haruka seemed to develop as a commander too quickly, but the growth was still solid so it was nice to see. Other than that the characters were developed okay. I felt for many their characters that had a lot more to them, but that seemed to have been not really shown as much here in favor of focusing on them in the other manga, which is a bit of a bummer. I did find it somewhat strange though how Mamoru was able to become comrades with people that were previously villains so easily. Working with them towards a common goal makes sense, but he seemed to actually become their comrade and him theirs, along with them not being as menacing as originally portrayed, which felt somewhat inconsistent. The art and designs beyond the really well drawn action were just okay. 

tl;dr: A manga that consistently has really strong action and battles, though with a plot that has scaling issues and main characters that while well developed on their own, don't seem to get developed together at all.